1. Field of the Invention
The present invention relates to a connecting rod or similar object for transmitting compressive or tensile stress, by transforming all or part of such stress into shearing-compressive stress, or even simple compression, comprising a fibrous tubular body, a connecting end member at one end of this body, a brace member which is rigid with the end member and comprises a truncated conical section on the exterior, an element which can be radially expanded and has a frusto-conical section with the same conicity as the frusto-conical section of the brace member, having an external diameter substantially equal to the internal diameter of the body of the connecting rod and mounted on the brace member and a cap with an internal diameter substantially equal to the external diameter of the tube.
2. Description of the Prior Art
Connecting rods or similar objects having a hollow body formed of fibres, for example of carbon fibres, and whose ends are fitted with connecting end members are already known.
In the prior art, a connecting rod of this type was formed by disposing a series of strips of fibrous material impregnated with resin on a mandrel of thermofusible material and also on the end member placed at the ends of the mandrel and by then proceeding to heat the resin. During this heating, the mandrel disintegrates or melts and only the body of the connecting rod remains.
It has recently been proposed to form the body of the connecting rod from man-made fibres. However, fixing the end members at the ends of the tube presents difficulties. This fixing can be practically performed only by adhesion. In order that this adhesion withstands to a sufficient degree both tensile stress and heat shock under load, it is necessary, in the present state of the art, to form the ends from titanium which is an expensive and rare metal. In addition, the form of these ends must be studied in detail (hence the complicated manufacture and machining) in order to enable the formation of an efficient mechanical anchorage independent of adhesive securement.
U.S. Pat. No. 3,638,979; discloses a force transmission device comprising a tube of fibrous material on one end of which a connecting end is secured. This end member is an integral part of a frusto-conical element; a number of wedges whose interior faces have the same conicity as the brace member and whose external faces are together cylindrical, with an outer diameter substantially equal to the inner diameter of the tube, are mounted on the brace member. A cap with an internal diameter substantially equal to the external diameter of the tube is mounted on the end of this tube.
This force transmission device does not resist compression well which is liable to result in the separation of the end member and slipping of the fibrous tube, which damages this tube.